Lighting Switch Pack (SP-19) Application Notes

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Lighting Switch Pack (SP-19) Quick Start Guide

This guide should help you to identify & properly connect the cards in your control box to your lighting and control systems. Based on the particular configuration you need for your application, your box will contain one interface card (either ‘control voltage’ or ‘DMX’ type), and 4 triac cards (4- or 8-channel regular capacity cards, or 4-channel high capacity cards). Click on pictures on this page to see a larger higher resolution picture. Before proceeding to connect your box, make sure to check the special note regarding DMX and phase wiring at the end of this guide to see if it applies to your situation.

16 channel control voltage interface cardCV Interface Card

16 channel control voltage interface card

This card takes up to 16 DC ‘control voltage’ (CV) inputs (on/off only), and translates them into inverted 5volt (TTL) signals for the triac cards. For inputs, this card is designed to be connected to any device that outputs 0-3 volts for an off signal, and 5-12 volts for an on signal. Simply connect the common (ground) line from your control device to one of the terminals marked ‘GND’, and connect your signal lines to the terminal inputs labeled with the channel you want to control. You can also use the terminals marked ‘GND’ and V+ as a 16V power source to run your own moderate-power-drain components (small control desks etc.)
The card/fan gets its operating power through wires running over to the triac cards, so once you’ve connected power to the triac cards (see below for help), the CV interface card & fan power up.

16 channel DMX decoder interface card

16 channel DMX decoder interface card

This card takes a standard DMX signal as an input and decodes it into 16 inverted 5volt (TTL) signals which then run up to 16 channels worth of triac cards (most commonly 4 cards x 4 channels each). Simply connect your 2 or 3 wire DMX source to the terminal marked ‘DMX IN’, and you’re done wiring this card. If you’re hooking into a ‘standard’ DMX XLR cable, Pin1 = Ground (shield or SH), Pin2 = -signal, and Pin3 = +signal. The card/fan gets its operating power through wires running over to the triac cards, so once you’ve connected power to the triac cards (see below for help), the DMX interface & fan power up.
First wire up your DMX input and power supply, then set your configuration mini-switches (see below for help), then turn on the power. If the card is powered & functioning properly but not receiving any DMX signal at it’s input, the LED will flash once every few seconds (saying “I’m awake, and DMX is timing out”). Once the card is receiving DMX commands, the LED comes on more or less steadily.

Setting the offset address switches

You will find 2 switch blocks on the DMX interface card – one with 8 switches & one with 4. The 8 switch block is for setting the DMX address offset. For example, if you have a 16 channel lighting box, and you want it to respond to channels 33-48 of your DMX controlling device, then you need an offset of 32. Turn on the switches to create the binary value of the offset you need. If you aren’t familiar with binary numbering, do it this way: Each switch has a number associated with it. Figure out which combination of the numbers will add up to the offset amount you need, and turn on the corresponding switches: sw1=1, sw2=2, sw3=4, sw4=8, sw5=16, sw6=32, sw7=64, sw8=128. So for example, if you need an offset of 40, 40 = 32+8, so you need to turn on switch 6 (32) and switch 4 (8). If you want it to respond to channels 17-32, you need only switch 5 on. For channels 1-16, leave all address switches off. Switch 3 of the 4 switch (‘Mode’) block adds an offset of 256, so turn it on if your offset needs to be more than 256.

Setting the other ‘Mode’ switches

The smaller block of 4 switches is used to set some other options available to you:

Switch 1 is reserved for future use – leave it off.

Turning on switch 2 turns off dimming and forces channels to be either fully on or fully off. We call this ‘Switch Mode’. If you need your control box to ignore partially dimmed signals, turn this switch on, and then any input signal over 50% will turn the channel on, and any signal under 50% will turn the channel off.

Turning on switch 3 adds 256 to the address offset. So for example, if (for some bizarre reason) you need an offset of 341, so that channel 1 in the box dims up when you slide up fader #342 on your DMX lighting control desk, turn on switches 1,3,5 and 7 of the address switch block, and turn on switch 3 of the Mode switch block. In this example, fader #350 would then control channel 9 of this box.

Switch 4 puts the DMX card into inverted output mode. If for some reason, you need an input signal of 100% to be turned into an output signal of 0% etc. (reversed), then turn this switch on.

Triac cards

Triac 8 switch Card
Triac 4 switch card
Triac 4 Switch Card Zoomed

Think of these cards as 4 or 8 remotely controlled dimming switches. The card takes a 110 volt input and turns that into 4 or 8 separate 0-110 volt (dimming) outputs, based on small electrical control voltages it receives from the interface card. To ‘wire up’ this card, connect the neutral (white) wire from your power source to any of the terminals marked ‘neutral’ or ‘N’ (near the center of the card), and connect a black line (also referred to as ‘hot’ wire) to at least one from each pair of line input terminals at either end of the terminal row. These are labeled ‘L’ on the 8 channel cards, and ‘LINE A’ and ‘LINE B’ on the 4 channel cards.
With 4 cards in a box, there is a total of 8 line inputs to be fed (2 per card). In a simple, low power situation, you can feed both sides of all 4 cards from the same source – just jumper all 8 points together, and connect your source wire to one of them. Or at the other extreme, if you need to, (perhaps you are dealing with low capacity circuit breakers, or you are controlling very high power lighting), you can feed each of the 8 input points from a separate power source. Just make sure your neutrals are always in fact neutral, and your hot wires are always hot.

This applies only if your box has the DMX interface card, and you are using dimming mode (not switch mode), and are using more than one power source to feed your box.

If the above statement applies to your situation, you have to make sure the box is wired so that all line inputs on the 2 left side cards are being fed from the same phase as each other, and that the 2 right side cards are fed from the same phase as each other. Otherwise, the dimming card will not properly sync to the 60hz sine waves, and will produce unpredictable dimming levels. (The left & right sides can be on the same phase or not, it doesn’t matter.) So, for example, if you are using a 220v 2 phase wiring scenario, both left cards should be fed from the same phase (say the black wire), and the same situation for the right (say the red wire). You can safely tie the neutrals (white) all together (assuming the building is properly wired – see ‘checking power sources’ below for help).
If you need to feed the upper card from a different power source (eg: breaker) than the lower card, that’s fine – just confirm that they are on the same phase. (again, see below for help) Remember – this only affects the smoothness of dimming – nothing else.


PLEASE NOTE: use this info at your own risk. This involves close proximity to live high voltage – only perform THESE TESTS if you are qualified and comfortable around such situations.

If you have 2 110 volt power sources in front of you and need to find out if they are on the same or different phases (ie: you can’t be sure where they are coming from), here’s how you do it using an AC voltmeter. Before turning on power, position all involved bare wire ends so that none are touching ANYTHING. With the power sources tuned (on, and not yet connected to the box,) carefully measure the voltage between the black wire from each power source (be VERY careful not to touch the wires with your fingers). If 2 110v power sources are on the same phase, you will see almost no voltage difference between their line (black wire) sides (typically 0 to 2 volts). If they are on different (opposing) phases, you will see roughly 220 volts. If you see roughly 110 volts of difference between the 2 black wires, something in the building is wired wrong – have someone rectify the problem before continuing.
Also, in a properly wired building, there will be almost no voltage between any neutral (white wire) and any ground (green wire, bare copper wire, metal box) If you find 110v or so, you have a dangerous backwards wiring problem. If you have ~8vac or more, you have a ‘very poor wiring’ situation. If you install a box in a ‘poor wiring situation’ (and I wouldn’t), expect problems & customer complaints to occur later. Alternatively, suggest that the wiring be replaced at least to the location of your box (if not entirely). In any case, DO NOT CONNECT ANYTHING WHERE THERE IS A WIRING ERROR PRESENT! (because if someone later corrects the wiring problem, box goes boom! Or walls go on fire! And guess who gets the blame!)

Finally, remember that getting shocked hurts, blowing up things costs money, and electricity can even kill you. If you are unsure about ANYTHING, please… please ask for some assistance from someone more experienced.

Thanks for reading this guide. If you’ve found it helpful, or if you have any questions or would like to make a comment, we’d love to hear from you.

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Current ratings:

Calculating the maximum load which can be connected to a triac box can be a little tricky since there are several limiting factors involved. The rating on each box will come down to the rating on each card in the box. Those ratings are:

4 Channel Cards:
Maximum current per channel: 9 Amps (Fuse rated for 10 amps)
Maximum power per channel: 1000 Watts
Total current per Ch.1&2 or 3&4: 15 Amps
Total power per Ch.1&2 or 3&4: 1800 Watts

8 Channel Cards:
Maximum current per channel: 3.6 Amps (Fuse rated for 4 amps)
Maximum power per channel: 432 Watts
Total current per Ch.1-4 or 5-8: 15 Amps
Total power per Ch.1-4 or 5-8: 1800 Watts

Note that the total current on the incoming power connector limits the card to less than the total of the channel ratings. This connector is rated for 15 Amps at 120 VAC which is less than the 2 x 10 Amp rating of the two channels. A mix of different sized loads (e.g. one 9 Amp and one 6 Amp load) can be used as long as the total does not exceed 15 Amps.

The maximum rating of the SP-19 box is two 15 Amp circuits per card times four cards per box for a total of a eight 15 Amp circuits. Keep in mind that the Canadian electrical code limits the load on each circuit protected by a 15 Amp breaker to 80% of 12 Amps.

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In general, fuses should be rated 20% higher than the maximum load that is being protected but that can be dropped to 10% with a slightly higher risk of premature fuse failure. While the individual channels for a four channel cards are designed for 10 Amps each, the fuse will fatigue and eventually fail if run at 10 Amps continuously. The recommended maximum is therefore 9 Amps which is 10% under the 10 Amp fuse rating. Similarly, the individual channels of the eight channel card are fused at 4 Amps, but again the load should not exceed 3.6 Amps to reduce nuisance blowing.

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3-Phase Power:

The SP-19 boxes are rated single phase power only but two legs of a 208 VAC circuit along with a neutral can be used as this results in 120 VAC across the load. The simplest connection is to wire one phase, say phase A to one side of a card and another phase, say phase B to the other side of the card. Connect the neutral of the incoming power to the neutral side of the load using the centre neutral terminals on the card. This arrangement has the advantage of reduced neutral current. The same idea can be used on 220/110 VAC power.

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Replacing triacs:

The ease of triac replacement is a key feature of the SP-19 triac boxes. The best method to determine triac failure is to measure the output voltage with a voltmeter. Keep in mind that the most common failure of triacs is to fail shorted so that the load never turns off. Triacs may also fail so that they pass only one half of the AC sine wave. When a bad channel has been identified:

  1. Mark the failed triac with a piece of tape or felt pen on the tab.
  2. Turn off the power at the breaker.
  3. Use a robertson screwdriver to remove the machine screw and hex nut.
  4. Slide the triac out of the socket.
  5. Apply silicone grease to the new triac. If there is none available, transfer grease from the failed triac. Don’t get the grease on your clothing – it’s tough to remove.
  6. Slide the new triac into the socket, line up the hole in the tab with the hole in the heat sink, replace the screw and tighten the nut.

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Substituting triacs:
Both 4 and 8 channel triac cards use the same triac which is rated for 15 Amps. 400 V in a TO-220 package with an isolated tab. Other triacs may be substituted in a pinch, but they must have an isolated tab. If there is any question about this, use an ohmmeter to check for a connection between the tab and the middle leg of the triac. If there is continuity, do not install the triac as there will be a direct short between the output of the triac and earth ground. When choosing a substitute, the voltage rating should be at least 300V. Triacs with lesser currents can also be substituted but choose a triac that is rated for at least 30% more than the load current. Trinity Electronics carries a good supply of triacs.

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Control inputs:

Trinity triac boxes have a buffer card which accepts a positive DC voltage between 0 and 15 volts. The buffer card, in turn, applies a +17 VDC, 30 mA signal to the LED side of the triac optocoupler. A red LED is wired in series to indicate when a channel is turned on to aid in debugging systems. A channel is turned on when the control voltage exceeds the buffer threshold of about 4 volts. The recommended range is 5 to 15 VDC to turn a channel on and 1 VDC or less to turn it off.

The buffer cards have been designed to operate in electrically noisy environments with long wire runs between the box and the controller. The input consists of a 1 Kohm resistor in parallel with 0.1 mfd capacitor to ground. This lower impedance reduces the sensitivity to the noise pick-up but this may be too big a load for some light controllers. If the controller cannot supply enough current (the maximum would be 15V/1Kohm=15 mA), the SIP resistors can be removed. The SIP is a long thin component with 10 leads which holds all eight resistors. There are two devices – one for channels 1 to 8 labelled N1 and the other for channels 9 to 16 labelled N2. The SIP N1 is located between U1 and J4 and N2 is between U2 and J5 (see the buffer card drawing). To remove without de-soldering, gently wiggle the SIP back and forth sideways until the leads fatigue and break off. This produces a clean break with no shorts between channels. If there is still too much impedance, the 0.1 mfd capacitors can also be removed. Use a pair of lead cutters and cut the lead flush to the board. Discard the capacitors as the leads will be too short to re-use. Remove only as many capacitors as required to preserve noise immunity for the remaining channels.

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Zero crossing control:

Zero crossing control means that the triac is turned on only when the AC line voltage passes through zero. The control signals from most controllers are asynchronous to the AC sine wave. Since it is not likely that any channel signal will arrive exactly at the zero point, the triac is not turned on until the next zero crossing. This is sometimes called zero point switching. A side effect of zero point switching is a delay of up to one half cycle (8.3 milliseconds) in turning a triac on but this is imperceptible for all but the very fastest chase patterns. Triacs only turn off during zero crossings but that is due to the nature of a triac and not the circuitry. Zero point switching is very desirable when switching resistive lamp loads because it reduces thermal shock on the lamp filament which results when a non-zero voltage is applied to the filament. With zero point switching, the filament is gently heated as the sine wave rises to a peak and then falls to zero again. The reduced thermal shock translates into longer lamp life.

The zero crossing feature in Trinity’s triac cards is incorporated into the triac opto-couplers. The MOC 3030 and the MOC 3031 optocouplers have zero crossing control built in whereas the MOC 3010 and MOC 3011 do not. The later devices turn on when the channel voltage goes high regardless of the instantaneous value of the line voltage. The parts ending in 1 (3031 and 3011) require less LED current than the parts ending in zero (3030 and 3110) but both can be used interchangeably in the Trinity triac cards. As explained below, non-zero crossing controlled optocouplers should be used for inductive loads such as lamps with built-in transformers.

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Inductive loads:

Inductive loads pose a problem for lighting control. Inductive loads incorporate coiled wire as part of their circuitry such as motors or transformers. In the lighting industry, the most common inductive loads are light fixtures with low voltage transformers built into the base. The first problem that inductive loads present is the phase shift between voltage and current. If the inductance is too high, a triac cannot turn off even when there is no gate drive. Trinity’s triac cards incorporate snubber circuits so that the triacs operate reliably on most inductive loads.

The second problem results when the drive signals create a situation where the triac turns on for an odd number of half cycles. A triac must be triggered at the beginning of both the positive going half of a sine wave and the negative going half. Under certain conditions, the triac will be repetitively turned on for 3, 5, 7, or 9 half cycles in a row. The extra positive or negative half cycle effectively create a DC component in the transformer primary winding. This creates overheating which can burn open the winding. The problem is generally created through the use of the zero crossing control circuitry which turns on triacs for complete half cycles.

This problem can be solved in two ways:

  1. Use a controller with integral cycle control which triggers the triac for an equal number of positive and negative half cycles.
  2. Use non-zero crossing optocouplers (MOC 3010 or MOC 3011) in the triac cards.

Some companies request only non-zero crossing optocouplers so that all triac boxes that they stock are suitable for transformer based lighting without having to check which components were used. The trade off is reduced life for standard resistive lamps.

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Matrix cards:

Matrix operation is a very simple but effective chasing arrangement. Lamps are arranged in a square of four columns and four rows. In X mode, the row triacs will chase with the four channel pattern and all the column triacs will be turned on steady.

In Y mode, the column triacs will chase and the four row triacs will be turned on. Like any four channel switching, lamps can be paralleled to 8, 12 or 16 rows and columns but the chase is still four channel. Both X and Y triacs can be turned on at the same time but there is a certain amount of ghosting which occurs when current finds a “sneak path” through several lamps in series. The result is a pattern of bright lights and several other lamps glowing with partial intensity. This mode looks good but may also appear to an installer like a partially failed triac.

Trinity has developed inexpensive matrix cards which provide switching for four hots and four lamp returns (effectively the lamp neutrals but to avoid approval problems we don’t use that term). Most applications will use two 4-channel cards – one card for switching the four hots and one for switching the four returns. The matrix card is very small and mounts in place of one of the 8-channel buffer chips on the buffer card. This will leave 8-channels of buffering for an additional matrix or more basic switching. The matrix cards require four chasing signals plus two additional lines: Y mode and X+Y mode (inputs 5 and 6 have no function – see the 16 channel buffer card drawing). With no signal present, the matrix defaults to X mode. When a control signal is applied to the Y mode line, the switching converts to Y mode. The X+Y mode chases both rows and columns simultaneously with the aforementioned ghosting effect. If both Y and X+Y lines are high, the Y mode will take priority. As with the other inputs, the recommended control voltages are 5 to 15 VDC. In most cases, a box can be retrofit for matrix operation in the field by installing one or more matrix cards and rewiring the triac cards.

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Allstar Show Industries Inc.
[email protected]

Axe Music
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